From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from relay.sgi.com (relay2.corp.sgi.com [137.38.102.29]) by oss.sgi.com (Postfix) with ESMTP id BB84C7CB0 for ; Wed, 23 Mar 2016 07:43:19 -0500 (CDT) Received: from cuda.sgi.com (cuda2.sgi.com [192.48.176.25]) by relay2.corp.sgi.com (Postfix) with ESMTP id 8D87C304051 for ; Wed, 23 Mar 2016 05:43:16 -0700 (PDT) Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) by cuda.sgi.com with ESMTP id qA8dnIML39Jn4ZYU (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO) for ; Wed, 23 Mar 2016 05:43:15 -0700 (PDT) Date: Wed, 23 Mar 2016 08:43:13 -0400 From: Brian Foster Subject: Re: Failing XFS memory allocation Message-ID: <20160323124312.GB43073@bfoster.bfoster> References: <56F26CCE.6010502@kyup.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <56F26CCE.6010502@kyup.com> List-Id: XFS Filesystem from SGI List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: xfs-bounces@oss.sgi.com Sender: xfs-bounces@oss.sgi.com To: Nikolay Borisov Cc: xfs@oss.sgi.com On Wed, Mar 23, 2016 at 12:15:42PM +0200, Nikolay Borisov wrote: > Hello, > > So I have an XFS filesystem which houses 2 2.3T sparse files, which are > loop-mounted. Recently I migrated a server to a 4.4.6 kernel and this > morning I observed the following in my dmesg: > > XFS: loop0(15174) possible memory allocation deadlock size 107168 in > kmem_alloc (mode:0x2400240) > Is there a stack trace associated with this message? > the mode is essentially (GFP_KERNEL | GFP_NOWARN) &= ~__GFP_FS. > Here is the site of the loop file in case it matters: > > du -h --apparent-size /storage/loop/file1 > 2.3T /storage/loop/file1 > > du -h /storage/loop/file1 > 878G /storage/loop/file1 > > And this string is repeated multiple times. Looking at the output of > "echo w > /proc/sysrq-trigger" I see the following suspicious entry: > > loop0 D ffff881fe081f038 0 15174 2 0x00000000 > ffff881fe081f038 ffff883ff29fa700 ffff881fecb70d00 ffff88407fffae00 > 0000000000000000 0000000502404240 ffffffff81e30d60 0000000000000000 > 0000000000000000 ffff881f00000003 0000000000000282 ffff883f00000000 > Call Trace: > [] ? _raw_spin_lock_irqsave+0x21/0x60 > [] schedule+0x47/0x90 > [] schedule_timeout+0x113/0x1e0 > [] ? lock_timer_base+0x80/0x80 > [] io_schedule_timeout+0xa4/0x110 > [] congestion_wait+0x7f/0x130 > [] ? woken_wake_function+0x20/0x20 > [] kmem_alloc+0x8c/0x120 [xfs] > [] ? __kmalloc+0x121/0x250 > [] kmem_realloc+0x33/0x80 [xfs] > [] xfs_iext_realloc_indirect+0x3d/0x60 [xfs] > [] xfs_iext_irec_new+0x3f/0xf0 [xfs] > [] xfs_iext_add_indirect_multi+0x14d/0x210 [xfs] > [] xfs_iext_add+0xc5/0x230 [xfs] It looks like it's working to add a new extent to the in-core extent list. If this is the stack associated with the warning message (combined with the large alloc size), I wonder if there's a fragmentation issue on the file leading to an excessive number of extents. What does 'xfs_bmap -v /storage/loop/file1' show? Brian > [] ? mempool_alloc_slab+0x15/0x20 > [] xfs_iext_insert+0x59/0x110 [xfs] > [] ? xfs_bmap_add_extent_hole_delay+0xd8/0x740 [xfs] > [] xfs_bmap_add_extent_hole_delay+0xd8/0x740 [xfs] > [] ? mempool_alloc_slab+0x15/0x20 > [] ? mempool_alloc+0x65/0x180 > [] ? xfs_iext_get_ext+0x38/0x70 [xfs] > [] ? xfs_iext_bno_to_ext+0xed/0x150 [xfs] > [] xfs_bmapi_reserve_delalloc+0x225/0x250 [xfs] > [] xfs_bmapi_delay+0x13e/0x290 [xfs] > [] xfs_iomap_write_delay+0x17d/0x300 [xfs] > [] ? xfs_bmapi_read+0x114/0x330 [xfs] > [] __xfs_get_blocks+0x585/0xa90 [xfs] > [] ? __percpu_counter_add+0x63/0x80 > [] ? account_page_dirtied+0xed/0x1b0 > [] ? alloc_buffer_head+0x49/0x60 > [] ? alloc_page_buffers+0x60/0xb0 > [] ? create_empty_buffers+0x45/0xc0 > [] xfs_get_blocks+0x14/0x20 [xfs] > [] __block_write_begin+0x1c2/0x580 > [] ? xfs_get_blocks_direct+0x20/0x20 [xfs] > [] xfs_vm_write_begin+0x61/0xf0 [xfs] > [] generic_perform_write+0xd0/0x1f0 > [] xfs_file_buffered_aio_write+0xe1/0x240 [xfs] > [] ? bt_clear_tag+0xb2/0xd0 > [] xfs_file_write_iter+0x167/0x170 [xfs] > [] vfs_iter_write+0x76/0xa0 > [] lo_write_bvec+0x65/0x100 [loop] > [] loop_queue_work+0x689/0x924 [loop] > [] ? retint_kernel+0x10/0x10 > [] kthread_worker_fn+0x61/0x1c0 > [] ? flush_kthread_work+0x120/0x120 > [] ? flush_kthread_work+0x120/0x120 > [] kthread+0xd7/0xf0 > [] ? schedule_tail+0x1e/0xd0 > [] ? kthread_freezable_should_stop+0x80/0x80 > [] ret_from_fork+0x3f/0x70 > [] ? kthread_freezable_should_stop+0x80/0x80 > > So this seems that there are writes to the loop device being queued and > while being served XFS has to do some internal memory allocation to fit > the new data, however due to some *uknown* reason it fails and starts > looping in kmem_alloc. I didn't see any OOM reports so presumably the > server was not out of memory, but unfortunately I didn't check the > memory fragmentation, though I collected a crash dump in case you need > further info. > > The one thing which bugs me is that XFS tried to allocate 107 contiguous > kb which is page-order-26 isn't this waaaaay too big and almost never > satisfiable, despite direct/bg reclaim to be enabled? For now I've > reverted to using 3.12.52 kernel, where this issue hasn't been observed > (yet) any ideas would be much appreciated. > > _______________________________________________ > xfs mailing list > xfs@oss.sgi.com > http://oss.sgi.com/mailman/listinfo/xfs _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs